The preparation of biomolecules, for example the separation of DNA from prokaryotic, eukaryotic and viral cultures, is an extremely precise, time-consuming operation which requires hours of skilled technician's time. Several procedures commonly used are disclosed in T. Maniatis et al., Molecular Cloning-A Laboratory Manual, Cold Spring Harbor Laboratory (1989).
These well known procedures are typically performed essentially manually. The technician adds the necessary reagents by pipeting, may accomplish the mixing by hand or with a vortex mixer, and may employ a fixed-speed centrifuge to perform the separations and pelleting. These procedures are not only time consuming, but because of the nature and extent of the technician's involvement, are prone to human error. As a result, the cost per separation is relatively high.
There exist numerous mechanical devices for performing some or all of the individual steps of these preparation techniques. For example, automated pipeting machines may be employed to relatively quickly and accurately add the desired reagents to the sample tubes. Separate mixing machines such as test tube inverters may also be used to accomplish some of the mixing steps. However, even if this process automating equipment is used, the entire preparation procedure still requires a relatively large number of distinct steps, each requiring at least a technician's guidance. Hence, the mechanical devices do not substantially reduce the cost per separation.